An image forming apparatus includes a developing device that accommodates a two-component developer that comprises a carrier and a toner. The image forming apparatus forms an electrostatic latent image on a surface of a photoconductive drum by supplying the two-component developer to the surface of the photoconductive drum. The developing device is filled with the two-component developer from a developer cartridge at the time of initial setup. During an operation of the image forming apparatus, the developing device is supplied with toner from a toner cartridge as needed. When the image forming apparatus is shipped, the developer cartridge and the toner cartridge are typically bundled with the image forming apparatus. Accordingly, there is a possibility that product cost may increase. Therefore, to suppress an increase in the product cost, it is conceivable to adopt a method in which the toner is accommodated within the developer cartridge separately from the developer rather than provided in a different cartridge. However, in this case, there is a possibility that the developer and the toner may be improperly mixed with each other inside the single developer cartridge.